sample.py

class SomeTypedDict(TypedDict):
    brands = forms.ModelChoiceField(required=True, queryset=None)


class MerchantBrandsForm(forms.Form, SomeTypedDict):
    fields: SomeTypedDict

    def __init__(self: merchant: Merchant, *args: Any, **kwargs: Any):
        super().__init__(*args, **kwargs)
        self.fields['brands'].queryset = merchant.brands.all()